1. Field of the Invention
The present invention relates to a zoom lens system.
2. Description of Related Art
Patent Literature Nos. 1 through 4 each disclose a zoom lens system configured of four lens groups, i.e., a zoom lens system configured of a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in that order from the object side, which aims to achieve a relatively small f-number at the short focal length extremity (wide-angle extremity) and to achieve a high zoom ratio of approximately 10:1.
However, since zooming burden on the third lens group is small in each zoom lens system of Patent Literature Nos. 1 through 4, either a desired zoom ratio cannot be attained, or the correction of various aberrations such as chromatic aberration and astigmatism is insufficient.
Although the zoom ratios in the zoom lens systems of Patent Literature Nos. 1 and 4 are relatively high, the f-number is only 3.5, which is insufficient.
Although the f-number in the zoom lens system of Patent Literature No. 3 is less than or equal to 3.0, which is relatively small, the zoom ratio is only approximately 7:1, which does not satisfy the requirement for a high zoom ratio.
Patent Literature 1: Japanese Unexamined Patent Application No. 2012-112996
Patent Literature 2: Pamphlet of International Publication No. 2011/102090
Patent Literature 3: Japanese Unexamined Patent Application No. 2014-85414
Patent Literature 4: Japanese Unexamined Patent Application No. 2013-44814